There is an increasing marketplace demand for low cost, high quality systems for distributing audio and video signals from a centralized source or service entrance. There is a particular need for using these distribution systems in residential and commercial applications to display entertainment and informational data services at various locations throughout a home or office.
The demand is present not only in new construction but also in retrofitting existing facilities with technologically advanced services and display equipment. Installing a system to distribute signals from a centralized source to multiple remote locations in an existing facility raises a number of problems. Keeping the costs of installation affordable requires working within the existing structural confines, Still, the installation must be aesthetically-pleasing and use the space available in an efficient manner.
Besides installation, there are other problems that the distribution system must overcome regardless of the facility. Ideally, the system must be able to distribute not only audio and video signals, but also a control signal. The control signal allows access to the centralized source from any of the remote locations in the facility. Besides transmitting different types of signals, the system must have the capability of handling multiple channels of the same signal type.
The various distribution systems which are based on wire technologies have failed to obviate these problems. The inherently smaller size of optical carriers provides an advantage over the problems caused by installing cables or wires through a facility.
Some prior art systems are available for distributing either audio or video signals over optical fibers. In frequency modulated (FM) systems, the coding is dependent on the time variations between peaks in the waveform, which also allows for higher levels of noise and distortion without depletion of signaling information. However, each video channel consumes about 30 mHz per channel and requires automatic gain control, demodulation, and then, conversion to an Amplitude Modulated (AM) signal for use with display monitors. The additional circuitry increases the equipment cost dramatically.
A broadband vestigial sideband AM system for video consumes only about 8 mMz per channel and requires no conversion for use with a display monitor. Noise and distortion from the equipment, however, directly affect the amplitude of any signals in a similar frequency range. Therefore, the AM transmission mode is more susceptible to noise and nonlinear channel distortions than the FM mode. These factors have limited the use of AM as a distribution format to transporting large numbers of channels such as the interconnecting of headends to hubs in cable television systems or a broadband local area network extension via very expensive distributed feedback laser diodes and single mode fibers.
A need remains for an affordable, reliable distribution system for audio and video signals for the home or office, The system must be able to control the distribution of the signals from a centralized source to multiple remote locations. The system must transmit signals of different types as well as multiple channels of the same signal type.